Roentgen discovered X-radiation by the inadvertent exposure of a silver halide photographic element. In 1913 the Eastman Kodak Company introduced its first product specifically intended to be exposed by X-radiation. Silver halide radiographic elements account for the overwhelming majority of medical diagnostic images.
The needs of medical diagnostic imaging have dictated the evolution of silver halide radiographic elements:
(1) The need to minimize patient exposure to X-radiation has led to the use of the high speed silver bromide and iodobromide emulsions. PA1 (2) The need to verify quickly that appropriate images have been obtained for diagnostic purposes has led to the creation of films that are compatible with rapid access processors. Reductions in processing times to substantially less than 90 seconds are being vigorously pursued in the art at this time. PA1 (3) The fact that silver cannot be reclaimed (as is customary in color photography, for instance) has led to film constructions that maximize silver covering power. PA1 (4) The need to produce images for medical diagnoses that have similar and familiar qualities to aid the radiologist's diagnosis, including features, such as image tone, that go more to image appearance than actual information content. PA1 (1) Rapid processing, allowing compatibility with rapid access processors (including those having dry-to-dry processing in less than 40 seconds) used for radio-graphic films; PA1 (2) High covering power, allowing low silver coating coverages; and PA1 (3) Enhanced image tone properties--that is, lower b* values when coated in films lacking blue dye incorporation and cold image tones with lower minimum densities when coated in films containing blue dye. PA1 n, p and q each independently represents 0 or 1; PA1 each L independently represents a methine group; PA1 L.sub.1 and L.sub.2 are substituted methine groups that together form a 5- or 6-membered carbocyclic ring (that is, the methine carbon atoms are linked by 1,2-ethylene or 1,3-propylene groups); PA1 R.sub.1 and R.sub.2 each independently represents an alkyl, sulfoalkyl or carboxyalkyl group (where the acid moieties can be present as a free acid, salt or ester); PA1 Y represents an amino or sulfonyl group; PA1 the alkyl moieties contain in each instance from 1 to 6 carbon atoms; and PA1 W is a counterion to balance the charge of the molecule. PA1 m is an integer of from 1 to 3, PA1 n and p are independently integers of from 1 to 6, PA1 Q.sup.1 and Q.sup.2 are ammonio groups, and PA1 X represents the ion or ions necessary to provide charge neutrality. PA1 HQ-1 Hydroquinone; PA1 HQ-2 Methylhydroquinone; PA1 HQ-3 2,6-Dimethylhydroquinone; PA1 HQ-4 Chlorohydroquinone; PA1 HQ-5 2-Methyl-3-chlorohydroquinone; PA1 HQ-6 Dichlorohydroquinone; PA1 HQ-7 Bromohydroquinone; PA1 HQ-9 Hydroxyhydroquinone; PA1 HQ-10 Potassium hydroquinone sulfonate. PA1 SDA-1 p-Aminophenol; PA1 SDA-2 p-Methylaminophenol; PA1 SDA-3 p-Ethylaminophenol; PA1 SDA-4 p-Dimethylaminophenol; PA1 SDA-5 p-Dibutylaminophenol; PA1 SDA-6 p-Piperidinophenol; PA1 SDA-7 4-Dimethylamino-2,6-dimethoxyphenol; PA1 SDA-8 N-Methyl-p-phenylenediamine; PA1 SDA-9 N-Ethyl-p-phenylenediamine; PA1 SDA-10 N,N-Dimethyl-p-phenylenediamine; PA1 SDA-11 N,N-Diethyl-p-phenylenediamine; PA1 SDA-12 N,N,N',N'-Tetramethyl-p-phenylenediamine; PA1 SDA-13 4-Diethylamino-2,6-dimethoxyaniline; PA1 SDA-14 Piperidino-hexose-reductone; PA1 SDA-15 Pyrrolidino-hexose-reductone; PA1 SDA-16 1-Phenyl-3-pyrazolidinone; PA1 SDA-17 4,4-Dimethyl-1-phenyl-3-pyrazolidinone; PA1 SDA-18 4-Hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidinone; PA1 SDA-19 4,4-Bis(hydroxymethyl)-1-phenyl-3-pyrazolidinone; PA1 SDA-20 4,4-Dimethyl-1-tolyl-3-pyrazolidinone; PA1 SDA-21 4,4-Dimethyl-1-xylyl-3-pyrazolidinone; PA1 SDA-22 1,5-Diphenyl-3-pyrazolidinone.
In recent years a number of alternative approaches to medical diagnostic imaging, particularly image acquisition, have become prominent. Medical diagnostic devices such as storage phosphor screens, CAT scanners, magnetic resonance imagers (MRI), and ultrasound imagers allow information to be obtained and stored in digital form. Although digitally stored images can be viewed and manipulated on a cathode ray tube (CRT) monitor, a hard copy of the image is almost always needed.
The most common approach for creating a hard copy of a digitally stored image is to expose a radiation-sensitive silver halide film through a series of laterally offset exposures using a laser, a light emitting diode (LED) or a light bar (a linear series of independently addressable LED's). The image is recreated as a series of laterally offset pixels. Initially the radiation-sensitive silver halide films were essentially the same films used for radiographic imaging, except that finer silver halide grains were substituted to minimize noise (granularity). The advantages of using modified radiographic films to provide a hard copy of the digitally stored image are that medical imaging centers are already equipped to process radiographic films and are familiar with their image characteristics.
A typical film, Kodak Ektascan HN.TM., for creating a hard copy of a digitally stored medical diagnostic image includes an emulsion layer coated on a clear or blue tinted polyester film support. The emulsion layer contains a red-sensitized silver iodobromide (2.5M % I, based on Ag) cubic grain (0.33 .mu.m ECD) emulsion coated at a silver coverage of 30 mg/dm.sup.2. A conventional gelatin overcoat is coated over the emulsion layer. On the back side of the support a pelloid layer containing a red-absorbing antihalation dye is coated. A gelatin interlayer, used as a hardener incorporation site, overlies the pelloid layer, and a gelatin overcoat containing an antistat overlies the interlayer. Developed silver is relied upon to provide in the infrared density required to activate processor sensors. No dye is introduced for the purpose of increasing infrared absorption.
It is the prevailing practice to process radiographic films and the film described above in 90 seconds or less. For example, the Kodak X-OMAT 480 RA.TM. rapid access processor employs the following processing cycle:
______________________________________ Development 24 seconds at 35.degree. C. Fixing 20 seconds at 35.degree. C. Washing 20 seconds at 35.degree. C. Drying 20 seconds at 65.degree. C. ______________________________________
with up to 6 seconds being taken up in film transport between processing steps.
A typical developer (hereinafter referred to as Developer A) exhibits the following composition:
______________________________________ Hydroquinone 30 g Phenidone .TM. 1.5 g KOH 21 g NaHCO.sub.3 7.5 g K.sub.2 SO.sub.3 44.2 g Na.sub.2 S.sub.2 O.sub.3 12.6 g NaBr 35.0 g 5-Methylbenzotriazole 0.06 g Glutaraldehyde 4.9 g Water to 1 liter/pH 10.0 ______________________________________
A typical fixer exhibits the following composition:
______________________________________ Sodium thiosulfate, 60% 260.0 g Sodium bisulfite 180.0 g Boric acid 25.0 g Acetic acid 10.0 g Water to 1 liter/pH 3.9-4.5 ______________________________________
Radiographic film processors such as RA 480 are capable of exposing large amounts of film over extended periods of time (e.g., a month or more) before its processing solutions are drained and replaced. Extended use of the processing solutions is made possible by the addition of small amounts of developer and fixer replenishers as each film is processed to compensate for developer and fixer losses by evaporation and film pick up.
Magnetic recording materials for incorporation in photographic elements are disclosed in Research Disclosure, Vol. 365, September 1994, Item 36544, Section XIV. Scan facilitating features, paragraph (2).